Procedure for obtaining derivatives from acetic acid

ABSTRACT

Procedure for obtaining acetic acid derivatives (I) where R 1  and R 2  are H or groups --CH 2  --COOH by oxidation of (II) where R and R&#39; are H or groups of --CH 2  --CH 2  OH with O 2  or a gas that contains it, in the presence of an metal hydroxide, demineralized water and Cu-Raney. The reaction is carried out keeping constant a partial pressure of oxygen below 20 Kg/cm 2 , inside the reactor. The acids (I) obtained as soluble salts, can be isolated and purified by chemical or electrochemical means. 
     Examples of acids (I) are glycine, iminediacetic acid and nitricetriacetic acid, useful as nutrients and in the synthesis of herbicides. ##STR1##

FIELD OF THE INVENTION

The invention concerns a procedure for obtaining derivatives of aceticacid, specifically glycine and iminodiacetic and nitrilotriacetic acidsby oxidizing monoethanolamine, diethanolamine and triethanolamine,respectively, with the use of oxygen or a gas that contains oxgygen anda Copper-Raney catalyst.

BACKGROUND TO THE INVENTION

The glycine, the iminodiacetic acid (I.D.A.) and the nitrilotriaceticacid (N.T.A.), described in numerous patents, are widely used indifferent sectors. For example, glycine can be used as a nutrient andboth I.D.A. and N.T.A. are used in the process of synthesizingherbicides, among other applications. Since these products have appearedon the market, a variety of ways of obtaining them have been describedand patented.

The Japanese patent 53/7709 held by the Mitsui Toatsu Chemical Co. Ltd,describes a procedure for obtaining I.D.A. and N.T.A. through theoxidation of diethanolamine and triethanolamine respectively, withoxygen gas in a base aqueous solution, using a noble metal (Pt and Pd)as catalyst for the reaction. Although the acids mentioned can beobtained through this procedure, the yield obtained for both I.D.A.(69%) and N.T.A. (60%), is rather low, and there is the added drawbackthat the possible losses of the noble metal used as a catalyst make thisprocess unprofitable from an economic point of view. On the other hand,it is a fact, recognised by experts in catalysis, that noble metallosses occur in catalytic processes both for acids and bases, throughthe solution of the metal in the reaction water, a complex process beingrequired for their recovery, and that there are also losses when theabove-mentioned catalysts are being handled. As a result, it isdifficult to make this type of process profitable considering that theend-products are of little economic value.

So, it would be useful if a process existed through which glycine andthe acids I.D.A. and N.T.A. could be obtained in such a state of purityand with sufficiently high yields resulting from oxidation of mono-, di-and triethanolamine, respectively, using a catalyst that was not a noblemetal (e.g. Copper-Raney), that the aforementioned economic shortcomingswould be reduced to a minimum.

Therefore, one of the aims of the invention is to provide a procedurefor oxidizing mono-, di- and triethanolamine, in the presence of aCopper-Raney catalyst, which gives good yields in the reactionperformance as well as minimizing cost of the catalyst when obtainingthe end-product.

On the other hand, other Japanese patents held by Nippon Catalytic Chem.Ind., 60/78.948, 60/78.949, 60/97.945, 60/100.545 and 61/65.840, providea procedure for obtaining glycine, I.D.A. and N.T.A. by oxidizing themono-, di- and triethanolamine in a base aqueous solution usingCopper-Raney as a catalyst, but with oxygen or gas that contains oxygen,obtained using a water decomposition reaction according to the followingreaction diagrams, respectively: ##STR2## In this procedure calculating,for example theoretically, the heat of the combustion and reactionrequired to obtain the iminodiacetic acid, this would be 2,053 Kcal/Kgof I.D.A. and the amount of hydrogen produced would be around 0.061 KgH₂ /Kg of I.D.A. So, for a load of 13.5 Kg of I.D.A. produced in 4 hoursusing the above-mentioned Japanese patent no. 69/78,948, the amount ofhydrogen released would be 0.81 Kg that, at 25° C. and 1 atmosphere,would be equivalent to 41 liters of hydrogen per minute, and this wouldhave to be allowed to leave the reaction so that it could be carried outat the pressure of 9 Kg/cm² which is referred to in the patent. So, inorder to adopt this procedure, it would be necessary to have fireproofinstallations, and to work in greater safety conditions due to thepresence of the hydrogen, and furthermore, the amount of heat to bedelivered would have a considerable effect on the final manufacturingcost of the end-products.

As a result of the aforementioned, a second aim of this invention is toprovide a mono-, di- and triethanolamine oxidation procedure in thepresence of a Copper-Raney catalyst, this type being the same as in thetwo previous procedures, but with the advantage of it not beingnecessary to carry out the procedure in fireproof installations, plusthe additional advantages of notably reducing the safety conditions forthe procedure and reducing to a minimum the heat expenses required tomanufacture the desired compounds.

The two aims of the procedure adopted for this invention arise from thenew technology for the manufacture of glycine, I.D.A. and N.T.A., whichare carried out according to the following reaction diagrams: ##STR3##which are slightly exothermic reactions, without releasing hydrogen andcarried out without the use of noble metals but with Copper-Raney as thecatalyst.

BRIEF DESCRIPTION OF THE INVENTION

The invention deals with a procedure for obtaining acetic acidderivatives, specifically glycine, iminodiacetic acid andnitrilotriacetic acid by oxidation with O₂ or a gas which contains it,of mono-, di- and triethanoamine respectively, in reactions carried outwith hardly any hydrogen and in the presence of a Copper-Raney catalyst.To bring about this reaction, it is suggested that the process shouldstart without any sweeping taking place with nitrogen or hydrogen, oncethe components of the reaction have been added and the heating begun forthe obtaining of the temperatures and pressures mentioned below. Inaddition, the catalyst to be used is Copper-Raney, wetted for safetyreasons.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a procedure for obtaining the acetic acidderivatives of general formula (I) ##STR4## where R₁ and R₂ can eitherbe H or --CH₂ --COOH groups independently.

The procedure for the invention can be represented by the followingreaction diagram in which Copper-Raney FIGURES as the catalyst. ##STR5##where R and R' can be H or --CH₂ --CH₂ OH groups independently.

As can be seen, when R=R'=H, the aminoalcohol (II) is themonoethanolamine and compound (I) obtained is the glycine (R₁ =R₂ =H).Likewise, when one of either R or R' is H and the other is --CH₂ --CH₂OH, compound (II) is the diethanolamine and the compound (I) obtained isthe iminodiacetic acid (one of either R₁ or R₂ is H and the other is--CH₂ --COOH), and when R=R'=--CH₂ --CH₂ OH, the compound (II) istriethanolamine and compound (I) obtained is nitrilotriacetic acid. Theabove reaction diagram n, can have the values 1, 2 or 3, respectively.

Thus the invention procedure includes the oxidation of an aminoalcoholin formula (II) ##STR6## where R and R' can either be H or --CH₂ --CH₂OH groups independently with O₂ or with a gas that contains O₂.

The reaction can be carried out at temperatures ranging from 25° C. to200° C., preferably between 150° C. and 195° C. It can take place at apartial O₂ pressure inside the reactor, at 20 Kg/cm², preferably between2 and 13 Kg/cm². Water is used as a solvent, and an alkalimetalhydroxide in a molar relation with respect to the hydroxide groups ofthe initial aminoalcohol (II) has been added, situated between 5% and20% in stoichiometric excess, preferably between 5% and 10%. This meansthat from 1.05 to 1.10 moles of alkalimetal hydroxide are used per molof monoethanolamine, from 2.10 to 2.20 moles of the hydroxide per mol ofdiethanolamine and from 3.15 to 3.30 moles of alkalimetal hydroxide permol of triethanolamine. An alkalimetal hydroxide can be used as long asthe salts formed with the acids obtained are soluble in the reactionenvironment. It is preferable that these salts are soluble in water at atemperature of 80°-95° C. Sodium hydroxide and potassium hydroxide areexamples of suitable Alkaline Hydroxides.

The initial concentration of the aminoalcohols (II) ranges between 20%and 35% in weight, with reference to the total initial weight of thecomponents of the reaction mass, preferably between 30% and 35% inweight. Larger concentrations can cause yield losses as a result ofdiffusion of the oxidant gas, and lower concentrations reduce theproductivity without improving the results. The catalyst used in theinvention procedure is Copper-Raney, although it is also possible to usea Nickel-Raney catalyst if small modifications are made in the process.The Copper-Raney catalyst can be easily manufactured through leachingwith sodium hydroxide in a reducing atmosphere of the alloy Al₂ Cu,following the procedures that have already been mentioned. The catalystis added in amounts less than the 30% weight of the initial aminoalcohol(II) content, preferably between 15% and 30% in weight, although with anaverage percentage of 25%, it is possible to obtain excellent results.

The oxidizing agent is oxygen or a gas containing oxygen such as air orsynthetic air, no more than the minimum amount necessary being used tomaintain the reaction of the above-mentioned partial pressure of O₂(less than 20 Kg/cm²), and no more than the gas necessary should be usedas a replacement.

The time the reaction takes, operating in these conditions, ranges from3.5 to 5.0 hours depending on the number of times the catalyst is used.

The reaction is monitored by measuring the conversion of the initialaminoalcohol (II) and the appearance of the acetic acid derivative (I).Once the reaction is completed, the reaction environment is subjected toa filtration process under heat, at a temperature of between 80° C. and95° C., preferably between 85° C. and 90° C., with a view to recoveringthe catalyst used, so that it can be regenerated and reused insuccessive reaction cycles.

After this, the base solution in the reaction environment, that whichcontains the soluble alkaline salts from the derivatives of the aceticacid, is subjected to an isolation and purification process so that thecorresponding acids from formula (I) can be obtained. This treatment canbe carried out either by chemical means, through crystalization of thereaction solution at temperatures ranging from 75° C. to 85° C.,preferably between 80° C. and 85° C., of the reaction solution after ithas been treated with hydrochloric acid, so as to obtain a pH of between0.5 and 2.5, depending on the acid obtained, or by electrochemicalmeans, applying the electrodialysis procedure referred to in the Spanishpatent no 9000130 (held by person who is applying for a patent for thisinvention).

The present invention can been clearly illustrated with the followingexamples, which should not be regarded as restrictive but simply servingas references, and which make it easier to understand the nature of theinvention procedure.

EXAMPLE 1

183 g. of 97% sodium hydroxide; 300 g. of demineralized water; 163.2 g.of 98% diethanolamine; 64 g. of Copper-Raney with a humidity level of30%, which really means using 44.8 g. of net-weight catalyst in thetest, and finally 40 further g. of demineralized water, to break downall the previous reagents, are all stirred into a stainless steelautoclave reactor (AISI 316) with a 1 liter capacity, and in theabove-mentioned order. Then, and while still stirring, the heatingprocess is started until 170° C. is reached and the pressure inside thereactor is 18 Kg/cm². At this stage, the reactor is brought into contactwith a shot of oxygen previously set at 18 Kg/cm² so as to have the samepressure and making sure that the pressure is kept constant during thecourse of the process, the oxygen consumed being continually replaced.The suspension is continuously stirred for 3.5 hours. When this time haselapsed, the reaction is concluded, and it is cooled to 90° C. andfiltered with suction with Buchner and Kitasato, regaining the humidityweight of 71.0 g. of the copper catalyst, this being kept for successivereuse after regeneration. The reaction solution, once analyzed bychromotography, provides a 95% yield of free iminodiacetic acid in theform of disodium salt, and this can be easily isolated and purifiedeither by crystalization at 85° C. at pH 22, or electrochemically usingone of the electrodialysis processes mentioned before. The purificationyield is quantitative (100%) using the isolation procedure andpurification by electrodialysis.

EXAMPLE 2

An experiment carried out with the same methodology as in Example 1, butusing 201.25 g. of 98.5% monoethanolamine; 144.3 g. of 97% sodiumhydroxide; 338.15 g. of demineralized water and 66.2 g. of Copper-Raneywith an approximate humidity of 25%, which amounts to 49.6 g. in netweight. The temperature of the reaction was 155° C. and the duration4.25 hours. The final yield of the reaction was 85.8% glycine. Theisolation and purification in this case, was carried out byelectrodialysis and a substantial purification yield was obtained.

The aim of the present invention having been described, the followingare stated as being essential to it.

We claim:
 1. A process for preparing amino acid salts represented by theformula: ##STR7## wherein R₁ and R₂ are independently selected from thegroup consisting of H and -CH₂ COOM, and M is an alkali metal, whichcomprises bringing together under reaction conditions an aqueoussolution of an aminoalcohol represented by the formula ##STR8## whereinR and R' are independently selected from the group consisting of H andCH₂ CH₂ OH, molecular oxygen or a gas containing molecular oxygen, analkali metal hydroxide and in the presence of a Raney copper catalyst.2. A process of claim 1 wherein the amount of Raney copper catalyst isbetween about 15 weight percent and about 30 weight percent, based onthe weight of the initial aminoalcohol present.
 3. A process of claim 1wherein the alkali metal hydroxide is sodium hydroxide or potassiumhydroxide.
 4. A process of claim 1 wherein the temperature of thereaction is between 25° C. and about 200° C.
 5. A process of claim 4wherein the temperature is between about 150° C. and about 195° C.
 6. Aprocess of claim 1 wherein the partial pressure of oxygen is betweenabout 2 and about 20 Kg/cm².
 7. A process of claim 6 wherein the partialpressure of oxygen is between about 2 and about 13 Kg/cm².
 8. A processof claim 3 wherein the aminoalcohol is monoethanolamine and the aminoacid salt is the alkali metal salt of glycine.
 9. A process of claim 3wherein the aminoalcohol is diethanolamine and the amino acid salt isthe di-alkali metal salt of iminodiacetic acid.
 10. A process of claim 3wherein the aminoalcohol is triethanolamine and the amino acid salt isthe tri-alkali metal salt of nitrilotriacetic acid.